My bike wont start - what to do?

[SO•Audiojack]

I doubt the oxygen sensor is responsible for not starting. The ECU runs in open loop mode until the engine is warm enough and doesn't use sensory data to control the mixture until that point.

Of course one thing to check is the engine temperature sensor, if it's broken it might output the maximum value (usually 255 celsius due to programming limitations) which leads to the ECU thinking the engine is (very ) warm. When the engine is cold it might not start if the ignition timing isn't corrected and the mixture enriched.

This knowledge comes from the car world but I doubt the engine management for modern bikes is that different. They're all 4-stroke fuel injected machines nonetheless.